A tire has two, laterally spaced bead portions which define the innermost diameter thereof. Each bead incorporates a metallic, ring sub-assembly which provides hoop strength and structural integrity to the bead--i.e.: the rim engaging structure of the tire. Each bead also normally includes an apex filler in addition to the metallic ring sub-assembly, because the combination assures a smooth transitional juncture between each bead and the adjacent side wall portion of the tire. To facilitate the manufacture of the tire, the ring sub-assembly and the apex filler are generally provided as a composite assembly about which the plies of the tire may be wrapped.
One prior art method of fabricating the combined ring and apex filler assembly applies a flat strip of elastomeric material along the inner circumference of a rubber coated, annular, ring sub-assembly and then encapsulates the ring sub-assembly by wrapping the strip radially outwardly about the wire ring sub-assembly. That portion of the strip which extends radially outwardly from the ring sub-assembly constitutes the apex filler. This method is fraught with difficulties, particularly in splicing the abutting ends of the wrapped strip. When the elastomeric strip is so wrapped to encapsulate the ring sub-assembly, the outer circumference of the material must stretch to accommodate the difference between the circumferential dimension of the ring sub-assembly and the circumferential dimension at the radially outer periphery of the strip. This stretching induces stresses which produce warpage in the form of dishing or scalloping along the radially outer portion of the resulting apex filler. This warpage is not constant from filler to filler, and it therefore increases the difficulty of maintaining quality control between successive tires employing bead assemblies made by this method.
Another known method of assembly applies an apex filler strip to a rotating bead ring until the starting point of the apex filler strip is adjacent the point at which the apex filler strip was first applied to the bead ring--approximately one revolution--at which time the apex filler strip is severed. The combined ring and apex filler assembly is then moved to a second processing station where a gripping and stretching apparatus engages the apex filler to close the ends. This also results in stretching the radially outer circumference of the apex filler strip more than that portion of the filler strip which has been joined with the bead ring. This stretching causes the same distortion problems inherent to, and as described in conjunction with, the previously discussed prior art method.